<!doctype html>
<html lang="zh-cn">
  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="/assets/bootstrap-4.4.1-dist/css/bootstrap.min.css">
    <title>Hello, world!</title>
    <style>
      .container > .row {
        height: 200px;
        background-color: gray;
      }
      .container > .row > div {
        height: 50px;
      }
      .container > .row > div:nth-child(1) {
        background-color: red;
      }
      .container > .row > div:nth-child(2) {
        background-color: yellow;
      }
      .container > .row > div:nth-child(3) {
        background-color: blue;
      }
      .container > .row > div:nth-child(4) {
        background-color: purple;
      }
    </style>
  </head>
  <body>

    <!-- 越大的越排在后面 -->
    <div class="container">
      <div class="row align-content-center">
        <div class="col-md-3 offset-3">
          第一部分
        </div>
        <div class="col-md-3 offset-3">
          第二部分
        </div>
      </div>
    </div>

    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
    <script src="./assets/bootstrap-4.4.1-dist/js/bootstrap.bundle.min.js"></script>
  </body>
</html>